The ultra-deep offshore operations considered as inevitable extreme conditions that modern oil & gas industry has to cope with. This paper will address some of the solutions for well known challenges: significant weight of riser structures, corrosion hazards and some of the drilling hazards. The focus is on opportunities, which are provided by (1) application of alternative material and (2) application of closed loop circulation system. The subjects are not interrelated, but presented under one title, because they target the same issues – reducing nonproductive time (NPT) and increasing safety of well construction. Lighter than conventional steel materials have been applied for riser design for decades: they were composite, titanium and aluminum alloys. In this paper we would focus on aluminum alloys, which have been used to develop all kind of tubular goods for the oil & gas industry, from drill pipe to tubing, casing, riser and pipeline. There is known positive experience with: ? Aluminum drilling riser used offshore Brazil and GOM since 2003; ? Aluminum Catenary Riser prototype developed in 2005-2009; ? Aluminum production casing set-up in the high hydrogen sulfide content environment in 2011. Structural aluminum alloys suitable for manufacturing tubular structures have a number of competitive properties in comparison with steel, which allows reducing structure weight and providing excellent corrosion resistance in different environments: Better than any other metal strength-to-weight ratio No brittleness at low temperatures; No hydrogen embrittlement (resistance in environments containing hydrogen sulfide and carbon dioxide); High overall corrosion resistance; Very good processing capabilities: machining, bending, pressing, extrusion, fusion welding. Availability of reliable light tubular material provides better opportunities and more “freedom” for riser and relevant structures design, but also allow for revisiting well construction criteria. The ability to use lighter riser, drill pipes, casing and tubing reduce rig equipment power requirements and time consumption. However these improvements could be lost if drilling hazards are not properly addressed. NPT caused by lost circulation, stuck pipe, borehole instability problems could lead to significant extra costs, which would negate lightweight structures application benefits. Borehole – riser system hydraulics in very deep waters caused significant problems narrowing the mud pressure window. The experience gained onshore for many years have proven that a closed and pressurizable mud returns system enables more precise wellbore pressure management. The large amount of high-resolution data, available during this process, is being used to support a variety of applications: Monitoring wellbore parameters Kick Loss detection and management Constant bottomhole pressure drilling Pressurized Mud-cap Drilling The paper presents some real results in offshore application of different managed pressure drilling scenarios, which allow mitigating hazards, increased safety and reducing NPT. The message of the paper – in today’s extreme exploration and field development environments industry needs complex approach from different prospective. Material engineering, mechanics and hydraulics experts need to work together for achieving the best possible results in terms of performance and safety.
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